It seems a few people are experiencing a problem with YouTube, where in either Google Chrome or Mozilla Firefox, it seems to keep downloading a file called "frame".
As Google doesn't seem to have sorted this problem - nor from what I can find out about it even addressed it - I have came across a cause and a solution for it. The solution will obviously have to be applied to both web browsers IF you're using both of them.
So, from what I can find out the cause of it is something to do with when your Google+ account is linked to your YouTube account (or vice-versa).
To solve this problem, you will need to:
1) Logout of YouTube (using the "Sign out" link at the top)
2) Clear your Cache (If you're using both browsers you will need to do it on both)
- Goto "Settings" in your Options Menu
- Scroll down and click "+ Show advanced settings"
- Click on "Clear browsing data"
- Make sure "Obliterate the following items from:" is set to the beginning of time", then select "Empty the cache"
- Hit the "Clear browsing data" button
- Goto "Options" in the "Tools" Menu
- Select "Advanced"
- Select "Network"
- Hit the "Clear Now" button within the "Cached Web Content" section
3) [Optional] Close and re-open your browser
4) Log back into your YouTube account.
The problem should now have been fixed.